Esterification



l Aug. 2', 1932.

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ESTERIFICATION Filed Feb. 4, 1927 PER CENT ENGL E4? als TIL L AWO/v Patented Aug. 2, 19,312

UNITED STATES PATENT; OFFICE EUGENE E. AYRES, JB., F SWARTHMORE, PENNSYLVANIA, ASSIGNOR T0 THE B. A. S.

v COMPANY, OF `PHILADELPHIA, PENNSYLVANIA, A CORPORATION 0F DELAWARE nsrnmrromrioiv Application filed February 4, 1927. Serial No. 155,87'8.

My invention relates lto esteriiication of alcohols and particularly to the production of mixtures containing esters of alcohols and alcohols and having a desired boiling range.A

A special application of my inventon resides in the production from mixtures of alcohols, of 'a mixture of esters and'alcohols that has a higher boiling -range than `a similar mixture produced by the ordinary processes of esterification, a special feature of my invention being the productionof a mixture of alcohols and esters that is substantially free of the lower boiling alcohols contained in the original mixture esteried. 'A' very important commercal aspect of my invention is that it is possible to produce thereby mixtures of esters and alcoholsv in commercially desired proportions and in which the alcohol fraction of the mixtures consists mainly of the higher boiling alcohols of the alcohol mixture from which the final mixture is produced. j n

My invention relates tothe esterification of mixtures of alcohols composed of various constituents. The mixture of alcohols esterified in accordance with'my invention may be a. mixture of several primary alcohols of different boiling points and ycontaining different numbers of carbon atoms, or a mixture of several secondary alcohols of dierent boiling points and having the same number 4 of carbon atoms, or a mixture of'l primary and secondary alcohols ,havingthe same number of carbon atoms, or a mixture of primary alcohols respectively having the same number of carbon atoms, or Vpractically any mixture of alcohols..l Special mixtures of-alcohols, the

esterification-'of which falls within my invention,`are various'mxtures of primary and secondary amyl alcohols primary and secondary butyl alcohols,l and primary and sec- -ondaryfhexyl alcohols, 'such mixtures includ- Cil ing theJ mixtures of alcohols obtainedA by the hydrolysis of corresponding chlorine substitution products;` `Other mixtures of alcohols from which commercially important mixtures of esters and alcohols may be produced may be made up tosuit requirements, a special example being a mixture of ethyl and butyl l alcohols.

I have found that the separation of alco- 'hols of different boiling points' may be car- 'mixture and alsol the alcohols from which the esters desired in thefinal mixture are produced. If the esterification of a mixture .of alcoliolsis carried as'ifar as possible in a single operation the products thereof will ,include esters and a residue of the lower boiling alcohols, causing the products of esterification to have high vapor pressure and a relatively low boiling range and a relatively large spread between initial and final boiling points. However, commercial requirements are such that it is desirable to havethe alcohol fraction of the ester-alcohol mixture consist as far as possible of-higher boiling alcohols and desirable that the mix- 'ture shall have a relatively high boilingrange and low vapor pressure and a'relativcly'small spread between the initial and final boiling points. As a specific example, it is pointed out that if an ester-alcohol mixture consisting of about 14% amyl alcohol and the/'balance of amyl esters, a proportion wellsuited to commercial requirements, ,is produced in one esterifying step from a suitable mixture of amyl alcohols, the alcohol fraction of the mixture will consist mainly vof the lowest boiling alcohols present in the .original mixture, Whereas Vthe ester-alcohol inixture is much more suitable to` commercial requirements if -the alcohol fraction thereof consists mainly of higher boiling alcohols of the original amyl alcohol mixture.

L'An important` feature of my invention is the productionpof ester-alcohol mixtures in lwhich the alcohol fraction consists of higher boiling alcohol presentcin the original alcohol mixture. In-accordance with my invention, after a suitable mixture of alcohols is made, the alcohol mixture is esterified to a degree less than that desired in the finished product, e. g., to a point at which the alcohol fraction constitutes about 30% of the mixture in a case where the alcohol fraction of the final mixture is to be about 14% thereof. The next step in the practice of my invention consists of removing from the products of the esterifying step, by rectification, lower boiling alcohols. Inasmuch as the alcohols form constant boiling mixtures with their esters, some of the lower boiling esters pass off with the lower boiling alcohols,

The residue will consist of esters in the desired proportion with an alcohol fraction composed chiefly, if not entirely, of higher boiling alcohols.

A further feature of my invention consists in mixing the fraction separated by rectiication, with an additional quantity of the alcohol mixture and then repeating the esterifying and rectifying step of my process, and ifdesired, continuing the process consisting in mixing the separated fractionv of each rectifying operation with additional fresh alcohol mixture and then esterif'ying and rectifying. In the practice of my invention the residues of successive' rectifying operations may beV brought together or kept separate and those residues may be purified by distillation to eliminate undesirable color and any decomposition products formed. In the practice of my invention the residue of the first rectification is such that the ratio of lower boiling alcohol to higher boiling alcohol is less than it is in the original alcohol mixture and the ratio of higher boiling esters to lower boiling esters is greater than the ratio of higher boiling alcohol to lower boil'- ing alcohol in the original alcohol mixture; and separated fractions of all rectification steps are such that the ratio of lower boiling alcohols to higher boiling alcohol is greater than it is in the original alcohol mixture and the ratio of higher boiling esters to lower boiling esters is much less than the ratio of higher boiling alcohol to lower boiling alcohol in the original alcohol mixture.

As the fractions separated by rectification are successively mixed with fresh alcohol Amixture in preparation'for the succeeding esterifying step, the operation reaches an equilibrium, and because of the return ofthe head products of rectification to successive esterlfication steps the residues ofthe successive rectifications, after the first, are such that the ratio of higher boiling esters therein to lower boiling esters therein is less than the ratio of higher boiling alcohols to lower boiling alcohol in the original alcohol. mixture. This condition occurs because the higher boiling alcohol of the original alcohol mixture is so largely used up in forming the alcohol fraction of the ester alcohol mixtures.

Ester-alcohol mixtures producedl in accordance wlth my inventlon, 1n comparison with simllar mixtures produced by esterifica- Vtion in a single step, have the same ester which 70% is primary alcohol and an acetate fraction of which is primary amyl kacetate, whereas production of a final product containing 86% of amyl acetate in accordance with my invention from the same original `mixture gives a product in which the alcohol fraction is substantially 100% primary alcohol and the acetate fraction consists of 64% primary acetate. Any undesirable 'effect resulting from reduction of the primary acetate percentage from 70 to 64 is very much more than compensated for by the substantial elimination of secondary amyl alcohol from the alcohol fraction. In commercial acetylation the prime object is vto obtain as high a conversion as possible of the acetic acid employed. By seeking only partial acetylation Athis object is attained because of `the unusually large 4excess of alcohol, whereas in seeking a maximum degree of es'terication the alcohol excess is reduced or the acetic acid may even be present in excess. Excess alcohol is easily recovered but whenthe excess is reduced the rate of reaction is low and when acetic acid is in excess its recovery is diiicult.. In general, in the production, in accordance with this invention, of a mixture of alcohols and esters, in which the esters constitute a desired proportion of the mixture, a mix-ture of alcohols having respectively different boilin points is subjected to esterification, and filiere isthereby produced a mixture of alcohols and esters in which the proportion of esters is not as high as the proportion of esters desired in the finalproduct. Then, by rectification, lower boiling alcohols are removed, and that operation incidentally carries away from the residue some of the lower boiling esters, but the rectifica-- tion is continued until the proportion of esters in the residue has been increased, by removal of alcohols, to the proportion desired in the final roduct. The proportion of esters desired in tlie final product will ordinarily be determined by the requirements of the trade in which the ester-alcohol mixture is em-4 ployed. For example, in the lacquer trade an ester-alcohol mixture comprising 85 per cent. of esters has been employed, and there is some demand for an alcohol-ester mixture comprisin 90 per cent. of esters when butyl esters an alcohols make up the mixture.

When the ester-alcohol mixture is made up of amyl alcohols and esters, a mixture comigh quality. In producing such a mixture, the esterification will be continued until the yesters constitute substantially less than 88 made by acetylation is an essential inter l mediate product in the practiceof my invention and a suitable intermediate product is a mixture of primary and secondary normal amyl alcohols and primary and secondary iso-amyl alcohols. I have found that a mixture of amyl alcohols produced by purifying the products of hydrolization of the products of chlorination of pentanes, is a suitable intermediate product for the production ofalcohol-ester mixtures in accordance with my invention, such a mixture of alcohols being readily produced by procedure in accordance with my Patents, Nos. 1,691.-

426, 1,717,136 and 1,717,393, by the practice of which mixtures of alcohols containing substantial proportions of normal alcohols and particularly primary normal alcohols can be produced.` I

In order to aid in the understanding of my invention,'Iv have shown in the single figure of the drawing hereto annexed, distillation curves of ester-alcohol mixtures having alcohol fractions of different compositions and constituting about 14% of the mixture. The

curve B is ,the distillation curve of an ester-` alcohol mixture in which the esters are amyl acetates and the alcohols are lower boiling amyl alcohols of the original-mixtures, las in ester-alcohol mixtures produced byesterification of an amyl alcohol mixture in a single step. lThe initial boiling point is low and the boiling range is low and the final boiling point is relatively low.

In the drawing, the curve A is the distillation curve of a mixture made in yaccordance with my invention and in which the acetates are amyl acetates and the alcohol fraction, forming about14% of the mixture, consists 'mainly of higher boiling alcohol of the original alcohol mixture. that 'the boiling range of the mixture is It will be .observed high and thatthe initialand. final boiling points are high and'thatthe spread'between lthe initia1and final boiling polnts is less than in the case where the alcohol fraction consists of lower boiling alcohols.-

u Mixtures of alcohols for use in the practice prising 88 per cent. of esters is a mixture of of my invention can be produced on a commercial scale. A desired hydrocarbon is obtained by distillation or rectification from gasoline roduced from natural gas. The' desired hy rocarbon or mixture of hydrocarbons may be chlorinated as set forth in my copending Patents No. 1,741,393 issued December 31, 1929, No. 1,835,202 to issue December 8, 1931, and No. 1,717,136 issued June 11, 1929. For example, the hydrocarbon or mixture of hydrocarbons, after vaporization,

if necessary, is passed, preferably at a velocity that will produceturbulent flow or a velocity of lthat order or at least a velocity in excess of one--half of the velocity that4 will produceturbulent flow, to a reactor heated to a suitable temperature, e. g. about 340 C. in the case of pentane, while chlorine vapor is introduced into the fiowing stream of hydrocarbon vapor preferably in a proportion of one i art of chlorine to 15 Lto 20 parts of hydrocarbon vapor, the reactor consisting of an externally heated conduit. The products of chlorination are thenproperly cooled and passed through a rectifier from which-the chlorinated product is withdrawn in liquid form and excess hydrocarbon passing olf as a vapor is condensed and a part of it is used as a reflux in the rectifier. yPreferably the fresh supply of hydrocarbons and condensed hydrocarbons that are to be passed 'again .through the chlorination step are dehydrated by acidulation, by hydrogen chloride, and removal of precipitated-moisture. The chlori-v nated hydrocarbons may then be hydrolized as set forth in my copending Patents No. 1, 691,425 and No. 1,691,426, issued November 13, 1928. rIvhus the hydrocarbon chloride may be introducedinto an iron autoclave together with alkaline salt of a substantially water-insoluble fatty acid, such as oleic, and

. heated for several hours until the reaction is substantially complete, the temperature being 150 C. in the case of amyl chloride. Then a fresh quantity of hydrocarbon chloridel and a fresh quantity of caustic soda solution are added, and the mixture, preferably stirreod by external circulation, is heated, for 3 or 4 hours. at 150 C. in the case ofy amyl chloride. The salt water forming in the bottom of the autoclave may be withdrawn and the alcohol may be'v removed by distilling. The residual oleic'ester having the basic radical of the hydrocarbon chloride under treatment is ready to receive a fresh charge of hydrocarbon chloride and caustic soda for a repetition of the process. When amyl chloride made as above-describedis hydrolized in lthis manner the crude product may be puri-' fied as' described in my copending application,.Ser. No. 165,877, filed FebruaryA, 1927,'

to. produce mixtures of amyl alcohols herein referredl to. Thus, by rectification, the crude mixture obtained .by the hydrolyzing step is dehydratediand the amyl chlorides are disiv l tilled off and then higher boiling chlorides are distilled off With sufficient Water present in the kettle ofthe rectifier to maintain moisture in the distillates at all temperatures up to the boiling point of' the lowest boiling desired alcohol. Then the desired mixture of alcohols is distilled off.

While I have described my invention by reference to particular substances and compositions, I do not intend to limit my invention thereto but intend that it shall include such variations and modifications as fall VWithin the hereunto appended claims. ,In this connection it is to be particularly noted that ester-alcohol mixtures having different alcohol fractions of different composition may be made in accordance With my invention. In this connection the point at which distillation in a rectifying tower is cut in order to achieve substantial removal of allr lower boiling alcohols and such esters as pass ofi therewith is readily determined in connection with any particular mixture of alcohols being esterified in accordance with my invention. In this connection I have found that the cut lnay be made at a temperature between 125o C. and 130 C., and preferably substantially at 130 C., in acetylating mixtures of amyl alcohol in accordanc'e with my invention.

What I claim and desire to secure by Letters Patent is:

1. In the production of a mixture in commercially desired proportions of alcohols and esters of alcohols, thel process compris'ng esterifying a mixture of aliphatic monohydroxy alcohols of different boiling points to a degree of esterification at which alcohol is present in the product in a proportion higher than that desired in the final product, and separating from-the product of esterification by rectification lower-boiling alcohols and such esters aspass off therewith until the residue contains alcohols and esters in the said commercially desired proportions.

2. In the production of a mixture in commercially desired proportions otalcohols and esters of alcohols, the process comprising esterifyinga mixture of aliphatic monohydroxy alcohols of different boiling points to a degree of esterification at which alcohol is present in the product in a. proportion greater than that desired in the final product, and separating substantially all low-boiling alcohols and some low-boiling esters from the products of esterification by rectification, leaving a -residual mixture of esters 4and higher-boiling alcohols that is substantially to a degree of esterification at which alcohols are present in the product in a proportion greater than that desired in the final product, and separating from the products of esterification by rectification a fraction in which the ratio of lower-boiling alcohol to higherboiling alcohol is greater than in the original alcohol mixture and the ratio of higherboiling ester to lower-boling ester is less than the ratio of higher-boiling alcohols to lower-boiling alcohols in the original alcohol mixture, said separation being continued until the alcohols and esters in the residue are in the said commercially desired proportion.

4. In the production of a mixture in commercially desired proportions of alcohols and esters of alcohols, the process comprising esterifying a mixture of aliphatic monohydroxy alcohols of different boiling points to a degree of esteri'fication at which the ratio of alcohol to esters in the product is greater than the said commercially desired proportion, and separating from the products of esterification by rectification a fraction containing lower-boiling alcohols and some lower-boiling esters, leaving a residue in which the ratio of lower-boiling alcohol to higher-boiling alcohol therein is less than in the original alcohol mixture and the ratio of higher-boiling ester to lower-boiling ester therein is greater than the ratio of higherboiling alcohol to lower-boiling alcohol in the original alcohol mixture.

In the production of a mixture 'in cornmercially desiredproportions of alcohols and esters of alcohols, the process comprising esterifying a mixture of ali hatic'monohydroxy alcohols of different oiling points to a degree of esterification at which the ratio of alcohol to esters in the product is greater than the said commercially desired proportion, separating from the products of esterificationby rectification lower-boiling alcohol .and such esters as pass off therewith until alcohols and esters present 'are in the commerciallydesired proportion, adding fresh alcohol aliphatic monohydroxy mixture to the separated fraction, and repeating the process with the resultant mixture.

6. In the production of a mixture in commercially desired proportions of alcohols and esters of alcohols, the process comprising esterifying a mixture of aliphatic monohydroxy alcohols of d1 fferent boiling points to a degree of esterification at which the ratio of alcohol to esters in the product is greater than the said commercially desired proportion, separating from the products of esterification by. reptificationlowerboiling alcoholand such esters.. as., p

mercially. desired proportions of alcoholsl and acetates of alcohols, the process comprising acetylating a Amixture of aliphatic monohydroxy alcohols of different boiling points to a degree of acetylation at which the ratio of alcohols to acetates in the product is greater than the commercially desired proportion, and` separating from the products .of acetylation by rectification lowerboiling alcohols and such acetates as pass olf therewith to produce a residue containing alcohols and acetates in said commercially desired proportion. Y

8. In the production of a mixture in commercially desired proportions of alcohols and acetates of alcohols, the process comprising acetylating a mixtureof aliphatic monohydroxy alcohols of different boiling points to a degree'of acetylation at. which the ratio of alcohols to acetates in the product is greater than the commercially'desired proportion, separating from the products of acetylation by rectiication lower-boiling alcohols 'and i such acetates as pass off therewith to producea residue-containing alcohols and esters in 4 commercially desired A proportion, adding vfresh alcohol mixture to the separated fraction, and repeating the'acetylating and rectifying operations with the resultant-mixture. 9. Inthe production 'of afmixture in corn-` lmercially desired proportions of amyl alcohols and amyl acetates, the process comprisl ingacetylating a-mixture of amyl alcohols to a 'degree of esterication at which the ratio. of alcohol -to esterin' the product is greater than the commercially desired proportion, and separating from the products of acetylation .by rectification' lower-boiling amyl alcohols and such amyl acetates as pass 0E therewith. d. e i y 10. In the production of a mixture in commercially desired proportions of amyl alcohols andamyl acetates, the process comprising-acetylating a mixture of amyl alcohols. to

a degreeof esterification at which the ratio l of alcohol to ester .in the product isv greater than A the. commercially desired proportion, separating fromv the products of acetylation by rectification lower-boiling amyl alcohols and such amyl acetates as pass oi therewith,"

and adding a fresh quantity of mixture of amyl alcohols to the separated fraction and repeating the a'cetylating and rectifying steps with the resultant mixture.'

.11. In the production of a mixture in commercially desired proportions of amyl alcohols and amyl acetates, fthe 4process comprising acetylating a mixture -of primary ,and vsecondary amyl alcohols to a degree of esteriof alcohols.

taining primary amyl alcohols and amyl acetates 'and substantially free of secondary amyl alcohols. p

12. In the production of a mixture ofalcohols and acetates of alcohols, the process comprising acetylating a mixture of aliphatic monohydroxy alcohols produced by hydrolysis ofa mixture of alkyl esters, continuing acetylation to a degree of acetylation at which the ratio of alcohol to ester in the product is greater than that desired in the inished product, and separating from the product of acetylation by rectification lower-boiling alcohols and such acetates as pass oi' therewith to produce a residue comprising acetates and alcohols and substantially free of lower-boiling alcohols of the original mixture.

' 13. In the productionof a mixture in commercially desired proportions of amyl alcohols and amyl acetates, the process comprising acetylating a mixture of amyl alcohols of diferent boiling points and. containing primary amyl alcohols to a degree ofesterica l-tion at which theratio of alcohol to ester in the product is greater than the commercially desired proportion, and separating from the product of acetylation byprectiication lowerkboiling amyl alcohols and such acetates as pass olf therewith to produce a residue con- .taining amyl acetates and higher-boiling amyl alcohols including primary amyl al` cohols of the original mixture of alcohols and substantially free of lower-boiling amyl al-.

v cohols of the original mixture of alcohols.

14. A composition comprising the distillation residue of the product obtained by sub jecting to esterifying treatment a mixture of 'alcohols ,of diiierent boiling points, said composition containing esters ofthe several A alcohols and higher-boiling alcohols of said mixture of alcohols and being substantially free of lower-boiling alcohols of said mixture 15. A composition comprising the distillaication at which the ratio` of alcohol to ester in the product is greater than the commercially desired proportion, and separatin from the product of acetylation by recti 4cation lower-boiling amyl alcohols and such acetates as pass oft therewith to produce a residue con- 'la t 

